The present invention relates to a terminal land frame, which substitutes for a conventional leadframe with radial leads and includes lands functioning as external terminals, and also relates to a method for manufacturing the same.
In recent years, to catch up with rapidly advancing downsizing of electronic units, it has become increasingly necessary to assemble semiconductor components, like resin-molded semiconductor devices, at a higher and higher density. Correspondingly, sizes and thicknesses of semiconductor components have also been noticeably reduced. In parallel with this downsizing trend, the number of pins required for a single electronic unit is also increasing day after day. To meet these demands, resin-molded semiconductor devices of a greatly reduced size and with a drastically reduced thickness should now be assembled at an even higher density.
Hereinafter, a conventional leadframe for a resin-molded semiconductor device will be described.
FIG. 24 is a plan view illustrating the structure of a conventional leadframe. As shown in FIG. 24, the conventional leadframe includes: a rectangular die pad 102; support leads 103; radial inner leads 104; outer leads 105; and tie bars 106, all of these members being provided inside a frame rail 101. The die pad 102 is used for mounting a semiconductor chip thereon. The support leads 103 support the die pad 102. The inner leads 104 are electrically connected to the semiconductor chip mounted with some connection means like metal fine wires. The outer leads 105 are joined to the respective inner leads 104 and to be connected to external terminals. The tie bars 106 are provided for joining and fixing the outer leads 105 together and for preventing the overflow of a resin encapsulant during a resin molding process.
It should be noted that an ordinary leadframe does not consist of a single pattern such as that shown in FIG. 24, but is made up of a plurality of such patterns, which are arranged to be connected together both horizontally and vertically.
Next, a conventional resin-molded semiconductor device will be described. FIG. 25 is a cross-sectional view illustrating a resin-molded semiconductor device using the leadframe shown in FIG. 24.
As shown in FIG. 25, a semiconductor chip 107 is mounted on the die pad 102 of the leadframe. The semiconductor chip 107 is electrically connected to the inner leads 104 via metal fine wires 108. The semiconductor chip 107 on the die pad 102 and the inner leads 104 are encapsulated with a resin encapsulant 109. The outer leads 105 protrude from the sides of the resin encapsulant 109 and the ends thereof are bent downward.
Next, a method for manufacturing the conventional resin-molded semiconductor device will be described with reference to FIG. 26. First, the semiconductor chip 107 is bonded, with an adhesive, onto the die pad 102 of the leadframe. This process step is called xe2x80x9cdie bondingxe2x80x9d. Next, the semiconductor chip 107 is connected to the respective ends of the inner leads 104 via the metal fine wires 108. This process step is called xe2x80x9cwire bondingxe2x80x9d. Subsequently, the semiconductor chip 107 and a portion of the leadframe inside the tie bars 106 (i.e., the inner leads 104 and so on) are molded with the resin encapsulant 109 such that the outer leads 105 protrude outward. This process step is called xe2x80x9cresin moldingxe2x80x9d. Finally, portions slightly inside the tie bars 106 are cut off to separate the outer leads 105 from each other and remove the frame rail 101, and the respective ends of the outer leads 105 are bent. This process step is called xe2x80x9ctie bar cutting and bendingxe2x80x9d. As a result, a resin-molded semiconductor device with the structure shown in FIG. 25 is completed. In FIG. 26, a region surrounded by the dashed line is to be molded with the resin encapsulant 109.
As described above, the number of devices that should be integrated within a single semiconductor chip, or the number of pins per chip, has been on the rise these days. In other words, the number of outer leads should also be increased to catch up with the latest trend. That is to say, the number of the inner leads, which are joined to the outer leads, should preferably be increased to cope with such an implementation. However, the width of the inner (or outer) lead has a processable limit. Thus, as the number of inner leads is increased, the overall size of the leadframe and that of the resulting resin-molded semiconductor device also increase. That is to say, it is difficult to realize a downsized and thinned resin-molded semiconductor device in such a case. On the other hand, if only the number of inner leads is increased to cope with the rise in number of pins of a semiconductor chip while using a leadframe of substantially the same size, then the width of a single inner lead should be further reduced. In such a case, it becomes more difficult to perform various process steps for forming the leadframe, like etching, as originally designed.
Recently, semi-face-mount semiconductor devices, such as ball grid array (BGA) types and land grid array (LGA) types, are also provided. A semiconductor device of such a type is mounted directly on a motherboard on the bottom. Specifically, first, a semiconductor chip is mounted on a carrier (i.e., a printed wiring board) including external electrodes on the bottom thereof. Next, the semiconductor chip is electrically connected to the external electrodes. And then the chip is molded with a resin on the upper surface of the carrier. The semiconductor devices of this face-mount type, which is mounted directly on a motherboard on the bottom, will be mainstream products in the near future. Accordingly, it is now clear that the conventional leadframe and resin-molded semiconductor device using the leadframe will soon be out of date under the circumstances such as these.
Also, the conventional resin-molded semiconductor device includes outer leads protruding outward from the sides of a resin encapsulant, and is supposed to be mounted onto a motherboard by bonding the outer leads to the electrodes of the motherboard. Accordingly, the conventional device cannot be mounted onto the board so reliably as the semiconductor devices of BGA and LGA types. Nevertheless, the semiconductor devices of the BGA and LGA types are more expensive, because these devices use a printed wiring board. That is to say, it is difficult for any of these conventional types of semiconductor devices to attain high reliability at a low cost.
An object of the present invention is providing a highly reliable resin-molded semiconductor device at a low cost by taking various measures to mount a semiconductor device onto a board on the bottom using a frame structure.
To achieve this object, the present inventors take a novel approach, which is totally different from that of the conventional leadframe structure. Specifically, the principal feature of the present invention lies in a frame structure including a plurality of xe2x80x9clandsxe2x80x9d to be external electrodes, which substitute for the radial xe2x80x9cleadsxe2x80x9d that have heretofore been adopted widely.
Another object of the present invention is manufacturing a resin-molded semiconductor device more easily and at a lower cost by eliminating the process steps of cutting and bending the leads.
A first exemplary terminal land frame according to the present invention includes: a frame body; a plurality of lands, each said land being substantially as thick as the frame body, at least part of each said land protruding out of the frame body; and a plurality of thinned portions, each said thinned portion connecting the frame body to associated one of the lands and being thinner than the frame body or the lands. When each said land is pressed in a direction in which the land protrudes, associated one of the thinned portions is fractured and the land is separable from the frame body.
A terminal land frame with such a structure is applicable to manufacturing a resin-molded semiconductor device in which part of each land, which protrudes from the lower surface of a resin encapsulant, can be used as an external electrode.
In one embodiment of the present invention, the top of that part of each said land, which protrudes from the frame body, is preferably laterally expanded and shaped like a mushroom.
In another embodiment, the frame body, the lands and the thinned portions are preferably all made of a single metal plate.
In still another embodiment, the top face of the part of each said land, which protrudes from the frame body, is preferably greater in area than another face of the land, which is opposite to the top face. And the top face preferably has curved edges.
A second exemplary terminal land frame according to the present invention includes: a frame body; a die pad being substantially as thick as the frame body and including a first part protruding out of the frame body; a plurality of lands, each said land being substantially as thick as the frame body and including a second part protruding out of the frame body; a first thinned portion connecting the frame body and the die pad together and being thinner than the frame body or the die pad; and a plurality of second thinned portions, each said second thinned portion connecting the frame body to associated one of the lands and being thinner than the frame body or the lands. When the die pad and each said land are pressed in a direction in which the die pad and the land protrude, the first thinned portion and associated one of the second thinned portions are fractured and the die pad and the land are separable from the frame body.
A terminal land frame including a die pad can also attain the same effects as those of the first terminal land frame.
The same preferred embodiments as those applied to the first terminal land frame are also applicable to the second terminal land frame.
A first exemplary method for manufacturing a terminal land frame according to the present invention includes the steps of: a) placing a metal plate, which will be wrought into a frame body, on a blanking die and pressing the metal plate downward with a presser die; and b) pressing a plurality of parts of the metal plate downward with a blanking member such that each of these parts pressed protrudes out of the body of the metal plate into associated one of openings of the blanking die, thereby forming a plurality of lands out of these parts and forming a plurality of half-cut thinned portions connecting the lands to the metal plate body.
According to the first method, the first terminal land frame of the present invention can be manufactured easily.
In one embodiment of the present invention, the blanking member preferably has a plurality of punches in the step a), each having a cross-sectional area smaller than that of associated one of the openings of the blanking die. And the step b) is preferably performed such that the top face of each said part, which protrudes from the metal plate body, is greater in area than another face of the part, which is opposite to the top face, and that the top face of each said part has curved edges.
A second exemplary method for manufacturing a terminal land frame according to the present invention includes the steps of: a) placing a metal plate, which will be wrought into a frame body, on a blanking die and pressing the metal plate downward with a presser die; and b) pressing a first region and a plurality of second regions of the metal plate downward with a blanking member such that a first part at the first region and a second part at each said second region protrude out of the body of the metal plate into associated openings of the blanking die, thereby forming a die pad at the first region, a half-cut first thinned portion connecting the die pad to the metal plate body, a plurality of lands at the second regions and a plurality of half-cut second thinned portions connecting the lands to the metal plate body.
According to the second method, the second terminal land frame of the present invention can be manufactured easily.
In one embodiment of the present invention, the blanking member preferably has a plurality of punches in the step a), each having a cross-sectional area smaller than that of associated one of the openings of the blanking die. The step b) is preferably performed such that the top face of the first part at the first region is greater in area than another face of the first part, which is opposite to the top face, and that the top face of the first part has curved edges. And the step b) is also preferably performed such that the top face of the second part at each said second region is greater in area than another face of the second part, which is opposite to the top face, and that the top face of the second part has curved edges.
A first resin-molded semiconductor device according to the present invention is formed by using a terminal land frame, which includes: a metallic frame body; a plurality of lands including first and second groups of lands, each said land being substantially as thick as the frame body, at least part of each said land protruding out of the frame body; and a plurality of thinned portions, each said thinned portion connecting the frame body to associated one of the lands and being thinner than the frame body or the lands. The semiconductor device includes: a semiconductor chip being mounted on the first group of lands and having a plurality of electrode pads; a plurality of connection members, each said connection member electrically connecting each said land of the second group to associated one of the electrode pads; and a resin encapsulant for molding the semiconductor chip, the connection members and respective upper halves of the lands, each said upper half corresponding to the part of the associated land that protrudes out of the frame body. The lower half of each said land other than the upper half thereof is not covered with the resin encapsulant but protrudes downward out of the lower surface of the resin encapsulant.
In this structure, the lower halves of the lands protruding out of the lower surface of the resin encapsulant can be used as the external electrodes, which can be disposed at arbitrary positions on the lower surface of the resin-molded semiconductor device. Thus, a highly reliable, thinned and downsized resin-molded semiconductor device can be manufactured at a lower cost by a high-density mount technique.
In one embodiment of the present invention, the top face of the upper half of each said land, which is buried in the resin encapsulant, is preferably greater in area than the bottom face of the lower half thereof, and the top face of the upper half preferably has curved edges.
A second resin-molded semiconductor device according to the present invention is formed by using a terminal land frame, which includes: a metallic frame body; a die pad being substantially as thick as the frame body and including a first part protruding out of the frame body; a plurality of lands, each said land being substantially as thick as the frame body and including a second part protruding out of the frame body; a first thinned portion connecting the frame body and the die pad together and being thinner than the frame body or the die pad; and a plurality of second thinned portions, each said second thinned portion connecting the frame body to associated one of the lands and being thinner than the frame body or the lands. The semiconductor device includes: a semiconductor chip being mounted on the die pad and having a plurality of electrode pads; a plurality of connection members, each said connection member electrically connecting each said land to associated one of the electrode pads of the semiconductor chip; and a resin encapsulant for molding the semiconductor chip, the connection members, a first upper half corresponding to the first part of the die pad protruding out of the frame body, and respective second upper halves corresponding to the second parts of the lands protruding out of the frame body. A first lower half, which is the remaining portion of the die pad other than the first upper half, and second lower halves, each of which is the remaining portion of associated one of the lands other than associated one of the second upper halves, are not covered with the resin encapsulant but protrude downward out of the lower surface of the resin encapsulant.
A resin-molded semiconductor device with such a structure can dissipate a sufficient amount of heat using the die pad and can also attain the same effects as those of the first resin-molded semiconductor device.
In one embodiment of the present invention, the top face of the first upper half of the die pad, which is buried in the resin encapsulant, is preferably greater in area than the bottom face of the first lower half thereof, and the top face of the first upper half preferably has curved edges. The top face of the second upper half of each said land, which is buried in the resin encapsulant, is preferably greater in area than the bottom face of the second lower half thereof, and the top face of the second upper half preferably has curved edges.
A third resin-molded semiconductor device according to the present invention is formed by using a terminal land frame, which includes: a metallic frame body; a plurality of lands, each said land being substantially as thick as the frame body, at least part of each said land protruding out of the frame body; and a plurality of thinned portions, each said thinned portion connecting the frame body to associated one of the lands and being thinner than the frame body or the lands. The semiconductor device includes: a semiconductor chip being mounted on the lands and having a plurality of electrode pads connected to the lands; and a resin encapsulant for molding the semiconductor chip and respective upper halves of the lands, each said upper half corresponding to the part of the associated land that protrudes out of the frame body. The lower half of each said land other than the upper half thereof is not covered with the resin encapsulant but protrudes downward out of the lower surface of the resin encapsulant.
A resin-molded semiconductor device with such a flip-chip mounted structure can attain the same effects as those of the first resin-molded semiconductor device.
In one embodiment of the present invention, the top face of the upper half of each said land, which is buried in the resin encapsulant, is preferably greater in area than the bottom face of the lower half thereof, and the top face of the upper half preferably has curved edges.
In another embodiment, the third resin-molded semiconductor device preferably further includes: the same number of protruding electrodes as that of the electrode pads of the semiconductor chip, each said protruding electrode being formed on associated one of the electrode pads; and a conductive adhesive for electrically connecting the protruding electrodes to the lands.
A first method for manufacturing a resin-molded semiconductor device according to the present invention includes the step of a) preparing a terminal land frame, which includes: a frame body; a plurality of lands including first and second groups of lands, each said land being substantially as thick as the frame body, at least part of each said land protruding out of the frame body; and a plurality of thinned portions, each said thinned portion connecting the frame body to associated one of the lands and being thinner than the frame body or the lands. When each said land is pressed in a direction in which the land protrudes, associated one of the thinned portions is fractured and the land is separable from the frame body. The method further includes the steps of: b) mounting a semiconductor chip on respective top faces of the protruding parts of the first group of lands; c) electrically connecting the lands of the second group to associated electrode pads of the semiconductor chip via a plurality of connection members; d) molding the semiconductor chip, the connection members and the upper half of the terminal land frame, including the respective parts of the lands protruding out of the frame body, with a resin encapsulant; and e) applying force in such a direction as separating the respective members molded with the resin encapsulant, including the lands, from the frame body, thereby separating a resin-molded semiconductor device, in which respective lower halves of the lands other than the protruding parts thereof are not covered with the resin encapsulant but protrude downward from the lower surface of the resin encapsulant, from the frame body.
According to this method, the first resin-molded semiconductor device can be manufactured easily while preventing resin bur from reaching the bottoms of the lands during resin molding and ensuring a standoff height large enough to use the lands as external electrodes.
In one embodiment of the present invention, respective faces of at least part of the lands, which faces are opposite to the top faces of the protruding parts of the lands, are preferably pressed toward the top faces in the step e).
A second method for manufacturing a resin-molded semiconductor device according to the present invention includes the steps of: a) preparing a terminal land frame, which includes: a metallic frame body; a die pad being substantially as thick as the frame body and including a first part protruding out of the frame body; a plurality of lands, each said land being substantially as thick as the frame body and including a second part protruding out of the frame body; a first thinned portion connecting the frame body and the die pad together and being thinner than the frame body or the die pad; and a plurality of second thinned portions, each said second thinned portion connecting the frame body to associated one of the lands and being thinner than the frame body or the lands; b) mounting a semiconductor chip on the top face of the protruding first part of the die pad; c) electrically connecting the lands to associated electrode pads of the semiconductor chip via a plurality of connection members; d) molding the semiconductor chip, the connection members and the upper half of the terminal land frame, including the first part of the die pad and the second parts of the lands, with a resin encapsulant; and e) applying force in such a direction as separating the respective members molded with the resin encapsulant, including the die pad and the lands, from the frame body, thereby separating a resin-molded semiconductor device, in which a first lower half, which is the remaining portion of the die pad other than the first part, and second lower halves, each of which is the remaining portion of associated one of the lands other than associated one of the second parts, are not covered with the resin encapsulant but protrude downward from the lower surface of the resin encapsulant, from the frame body.
According to this method, the second resin-molded semiconductor device can be manufactured easily while preventing resin bur from reaching the bottoms of the lands during resin molding and ensuring a standoff height large enough to use the lands as external electrodes.
In one embodiment of the present invention, a face of the die pad, which face is opposite to the top face of the first part, is preferably pressed toward the top face, and respective faces of at least part of the lands, which faces are opposite to the top faces of the second parts, are preferably pressed toward the top faces in the step e).
A third method for manufacturing a resin-molded semiconductor device according to the present invention includes the step of a) preparing a terminal land frame, which includes: a metallic frame body; a plurality of lands, each said land being substantially as thick as the frame body, at least part of each said land protruding out of the frame body; and a plurality of thinned portions, each said thinned portion connecting the frame body to associated one of the lands and being thinner than the frame body or the lands. When each said land is pressed in a direction in which the land protrudes, associated one of the thinned portions is fractured and the land is separable from the frame body. The method further includes the steps of: b) mounting a semiconductor chip on respective top faces of the protruding parts of the lands, thereby electrically connecting the lands to associated electrode pads of the semiconductor chip; c) molding the semiconductor chip and the upper half of the terminal land frame, including the respective parts of the lands protruding out of the frame body, with a resin encapsulant; and d) applying force in such a direction as separating the respective members molded with the resin encapsulant, including the lands, from the frame body, thereby separating a resin-molded semiconductor device, in which respective lower halves of the lands other than the protruding parts thereof are not covered with the resin encapsulant but protrude downward from the lower surface of the resin encapsulant, from the frame body.
According to this method, the third resin-molded semiconductor device can be manufactured easily while preventing resin bur from reaching the bottoms of the lands during resin molding and ensuring a standoff height large enough to use the lands as external electrodes.
In one embodiment of the present invention, respective faces of at least part of the lands, which faces are opposite to the top faces of the protruding parts of the lands, are preferably pressed toward the top faces in the step d).
In another embodiment, protruding electrodes, which are formed on the respective electrode pads of the semiconductor chip, are preferably electrically connected to the lands with a conductive adhesive in the step b).